Throughout U.S. history, minorities have had an unequal voice in politics — because they were denied the right to vote, or because when they could vote they had to pay poll taxes, or because, in the absence of poll taxes, even subtler obstacles, such as gerrymandering, emerged.

For the most part, we think that such barriers have been receding with time. But the left-leaning think tank Demos argues that another factor is further restraining the political power of minorities today: our system of big-money spending in elections. Why? Winning candidates today for all kinds of offices are largely backed by big sums from a small number of people. And because minorities are underrepresented in that high-spending group — and among the very high-income in general — their interests tend to be unrepresented as well by candidates overwhelmingly funded by wealthy white donors.

By this thinking, as the power of money in politics rises, unleashed by a series of court decisions, the power of groups that can't afford to influence elections with their pocket books will wane. As a result, writes Demos policy advocate Adam Lioz in a new report, "our big money campaign finance system entrenches political inequality for people of color."

Put another way, it enhances the influence of people with money, who are disproportionately white:

In effect, two things happen when the political system limits the power of people without much money: Minority candidates are less likely to run for office, to raise enough money when they do, and to win as a result. And the candidates who do win are less likely to support policies prioritized by minority communities like criminal justice reform, minimum wage increases, or paid sick days.

If anything, Lioz argues, candidates backed by the rich may support policies that undermine progress on racial inequality, like overincarceration or bank deregulation that enables predatory lending.

Individual campaign donations aren't typically reported by race. But large donors are more likely to be wealthy, male and white than the population at large. And polling data confirm that the wealthy often have different policy priorities than the poor, the general population and minorities: They're more likely to value deficit reduction over job creation, and they're less likely to support raising the minimum wage. Minorities and the poor, meanwhile, are much more likely to say that the government should pursue policies reducing the wealth gap.

Census data can also tell us something about the communities where donors live, even if we don't know their exact demographics. In the 2012 election cycle, for instance, more than 90 percent of donations of $200 or more to presidential campaigns came from majority-white neighborhoods.

Data also suggest that the large pool of people who give small donations is more diverse than the small pool of people who give the really big bucks. That means that we could partly address the problem Demos raises through programs that match small donations with public money, amplifying the power of voters who don't have a lot to give.

Lioz points to one such example: Connecticut established a public-financing system in 2008 to match small donations. In 2010, progressive Dannel Malloy, who benefited from such donations, won the governor's race. In that campaign, he supported paid sick leave for workers, in contrast to his opponents. The next year, Connecticut became the first state to pass a law requiring most employers to offer paid sick leave. Perhaps that would have happened without a campaign finance system that empowers people who can't afford to be big donors. But it's also plausible that a candidate carried to office by people who don't need paid sick days would be less likely to fight for them.